This is this is the shape I am trying to achieve. The upper and lower horizontal surfaces are 6" radius curves. My problem is how to deal with the triangular vertical surface.
Just looking at the top: There is only 6.7" between the top of the hood and the top of the body and there is 6.5" of curves doing upwards (4" + 2.5"). However, with the 6" rounding on the front edge, the greatest length from the horizontal to the top of the hood is 5.9772".
From the photo, it looks like the horizontal radius drops quickly from 6" to 1.5" and that smaller radius continues up and an along the top.